What if Sonic and Mario's fortunes were reversed?

We all know the story. Mario was great, then Sonic was newer, then Mario was great then Sonic was worse, then it was Mario Week on GamesRadar... But what if things had gone the other way? What if it was Mario who suffered a decade of missteps while Sonic went from strength to strength, trailblazing his way into gaming history by constantly reinventing himself like a spiny, blue… er… Madonna. Let's see how that might have panned out if the roles were reversed...